import java.util.*;

public class Main {
    //小球反弹

    public static boolean check(int a, int b) {
        if((a % b) == 0 && (a / b) % 2 == 0){
            return true;
        }
        return false;
    }

    public static void main1(String[] args) {
        long t = 1;
        int x = 343720;
        int y = 233333;
        while(true){
            int LB = 15 * (int) t;
            int LC = 17 * (int) t;
            if(check(LB,x) && check(LC,y)){
                break;
            }
            t++;
        }
        System.out.printf("%.2f\n",Math.sqrt(15*t*15*t+17*t*17*t));
    }


    public static void main2(String[] args) {
        int ans = 0;
        for(int i = 0; i <= 50; ++i){
            for(int j = i + 1; j <= 50; ++j){
                if(i <= 7 && j <= 7){
                    ans += 0;
                }else{
                    ans++;
                }
            }
        }
        System.out.println(ans);
    }

    //判断两数是否互质？
    private static int gcd(int a,int b){
        if(b == 0) return a;
        return gcd(b,a % b);
    }

    //若gcd(a,b) == 1，则两数互质

    public static void main(String[] args) {
        System.out.println(cala(50) - cala(7));
    }

    private static int cala(int n){
        return n*(n - 1) /2;
    }
}
